Permanent magnet rotor arrangements are often used in applications, wherein low-speed large-diameter electrical generators are employed, like, for example, wind turbine generators.
Such a permanent magnet rotor arrangement is known from EP 1 860 755 A2. The rotor arrangement described therein includes a rotor having a radially outer rim. A circumferential array of magnet carriers is affixed to the outer rim, wherein the magnet carriers have a radially outer surface. An inverted U-shaped pole piece retainer made of nonmagnetic material is affixed to each magnet carrier forming an axially extending channel, wherein pole pieces of a permanent magnetic material are located adjacent to the magnetic carriers in the channels.